Electrotherapy devices are used to provide electric shocks to treat patients for a variety of heart arrhythmias. For example, external defibrillators provide relatively high-energy shocks to a patient, usually through electrodes attached to the patient's torso, to convert ventricular fibrillation to a normal sinus rhythm. Similarly, external cardioverters can be used to provide shocks to convert atrial fibrillation to a more normal heart rhythm. In this application, the term "electrotherapy device" includes devices performing only a monitoring function.
Event data means information that can be related to particular intervals of time. The time intervals may be "elapsed time," i.e., time related to a reference event, such as power-up of the data collecting device or start of the data collection process. The time intervals may instead be synchronized with a master standard, such as Greenwich mean time or an arbitrarily selected timekeeper, in which case the time is known as "synchronized time." Accepted time units (seconds, minutes, etc.) are used to measure both elapsed time and synchronized time.
One example of event data is an electrocardiograph showing a patient's heart electrical activity, which may be plotted versus elapsed time from a starting or triggering event. Event data also includes the raw data upon which the plots or graphs are based, whether in digital, analog or any other form. The event data may be a continuous data stream, a discontinuous series of events, or a combination of continuous data and discrete events.
Prior art electrotherapy devices record event information and time information collected from the patient, reported by the device and/or otherwise collected from the devices' surroundings (such as audio information, including the voices of the devices' operators) during the operation of the device. This and other information collected by an electrotherapy device may be referred to collectively as "electrotherapy information". For example, the Laerdal Heartstart 3000 external defibrillator records patient ECG and information about the defibrillator in a solid state memory module. This patient and ECG information can be later retrieved from the memory module using suitable software. As another example, the Marquette Responder 1500 external defibrillator stores event data such as patient ECG on a data card inserted into a data card slot in the defibrillator. The event and time data regarding the patient's physiological condition may be logged to provide information to later caregivers about the patient and about the care the patient received, such as the time required for the emergency medical technicians to reach the patient and the patient's response to the treatment.
Event data collected from electrotherapy devices may be analyzed to extract useful time-based information. Part of the event data analysis often requires reference to a local clock by the data user to place the time stamped on the collected event in the context of the data user's time. For example, if a portion of the collected event indicates that the event occurred at 4:00 PM, the data user must assume that the electrotherapy device clock and the data user's local clock indicated "4:00 PM" at the same time. In other words, the data user must assume that the electrotherapy device clock and the data user's local clock are synchronized. In addition, the data user must assume that the electrotherapy device's measure of a second or a minute is the same as the data user's local measure of a second or a minute so that the recorded time (whether elapsed time or synchronized time) may be interpreted in a meaningful way.
The synchronized time indicated by a device's clock may drift from the synchronized time indicated by the master timekeeper because of environmental conditions, mechanical problems, or other reasons. Also, the act of setting the electrotherapy device clock could introduce discrepancies between the time indicated by the device's clock and the time indicated by the data user's clock, especially if the data logger clock is set by hand, or if the electrotherapy device's clock was not initially synchronized to the data user's clock prior to event data collection. These problems are compounded if a single data user receives event data from multiple electrotherapy devices, since each electrotherapy device clock may have been affected in different ways by environmental conditions, errors in initial setting, and the like. Thus, when the accurate logging of synchronized time is important, a relatively expensive clock and elaborate and/or expensive time setting procedures may have to be included in the electrotherapy device.
When emergency response personnel are called to the scene of a cardiac arrest, a report of the incident is desirable from several standpoints. First, many jurisdictions require emergency response personnel to file such incident reports, detailing the condition of the patient and the type of treatment delivered. Second, from the standpoint of accurate diagnosis and subsequent treatment, it is desirable to note the various treatments applied at the scene and record the patient's response. Such information might help trained cardiologists, sitting in review of the incident, to rule out certain disease or defect conditions that potentially afflict the patient.
Paramedics and other emergency medical response personnel are often the first on the scene and are usually sent out to the patient from a central dispatch in response to a "911" call or other emergency calling service. These personnel typically carry portable external defibrillators to treat patients suffering from sudden cardiac arrest. Most currently available portable defibrillators have some means for collecting and storing information concerning the patients and the type of treatment delivered to the patient. For example, prior art defibrillators record the patient's ECG as well as the conversation of the response personnel and other sounds of the incident in progress.
Much of the information, however, is recorded in incident reports that are generated and compiled manually by the response personnel after rendering treatment at the scene. Additionally, the presentation of compiled data does not allow for a robust means of identifying and accessing particular data that occurred at particular points in time (called "events"). U.S. Pat. No. 4,610,254 to Morgan et al. discloses a portable interactive defibrillator that records patient status information such as ECG as well as user-supplied information that is input in the form of prompts from the defibrillator to the user. Morgan further discloses the use of a tape recorder medium to record relevant medical information during the use of device. The recorder is a two-track recorder--one track for ECG and other patient data and the second track for audio data to record the voice of the response personnel as well as sounds indicating that a shock has been delivered to the patient.
U.S. Pat. No. 4,945,477 to Edwards discloses a system for recording and presenting information pertaining to a medical event such a cardiac arrest. Edwards' system records events identified by the defibrillator and stores these events for human-readable replay. Defibrillator-identified events (termed "annotations") can be effected by the pressing of a button on the defibrillator by the user or by the recognition that a medical event (e.g., arrhythmia) has occurred. As a memory space saving technique, Edwards describes a means in which his system stores three second intervals according to priority of events. Events having higher priority may well overwrite events of lower priority.
U.S. Pat. No. 5,277,188 to Selker discloses a clinical information reporting system that inputs both ECG-related and non-ECG-related (e.g. laboratory test results such as blood enzymes, urinalysis, blood pressure, and the like) patient cardiac data into a database. Selker's database maintains such data for a group of patients, typically admitted at a health care facility. Information stored in the database allows a user to classify patients into meaningful clinical classes and generate reports concerning the process of care for cardiac patients.
While these systems do provide some level of data recording and play-back, they do not provide a full range of event identification and presentation that would be useful for trained medical personnel to quickly assess an individual patient's condition, particularly soon after a cardiac arrest. For example, in a recorded 10-20 minute emergency response, instead of requiring a reviewing cardiologist to view the entire response to get to the events of interest, it would be useful for the cardiologist to "jump" directly to certain events (e.g. times where shock has been administered to the patient). Additionally, it would be useful for trained personnel to manually identify and annotate certain points in time as events--particularly for events that would not necessarily be automatically recorded by the device (e.g., the time when certain drugs have been administered to the patient).
Thus, it is an object of the present invention to provide medical personnel with a system that quickly and accurately allows random access to events that occurred during the course of an emergency response.
It is another object of the present invention to allow users to manually input and annotate events that occur during a response and have those manually-input events randomly accessible during playback.